Centrifugal development apparatus and method

ABSTRACT

An apparatus for developing an electrostatic latent image which includes a housing rotatable about an axis for conveying developer to the image. The housing includes a sloped inner surface which increases in distance from the axis in an upward direction and includes a top surface which lies in a plane substantially perpendicular to the axis to confront an electrostatic image to develop. Rotation of the housing centrifugally impels developer from the bottom of the housing along the inner sloped surface to the top surface of the housing in order to develop the image.

United States Patent Donalies [54] CENTRIFUGAL DEVELOPMENT APPARATUS ANDMETHOD [4 1 May 23, 1972 3,130,066 4/1964 Brady ..118/627 X 3,349,75010/1967 Donalies... 18/637 3,435,803 4/1969 Donalies ....1 17/1 7.53,367,307 2/1968 Lawes et al.. l8/312 X 3,536,043 10/1970 Eppe et a]...118/637 Primary Examiner-Mervin Stein Attomey-Donald F. Daley, JamesJ. Ralabate and James P. OSullivan I [57] ABSTRACT An apparatus fordeveloping an electrostatic latent image which includes a housingrotatable about an axis for conveying developer to the image. Thehousing includes a sloped inner surface which increases in distance fromthe axis in an upward direction and includes a top surface which lies ina plane substantially perpendicular to the axis to confront anelectrostatic image to develop. Rotation of the housing centrifugallyimpels developer from the bottom of the housing along the inner slopedsurface to the top surface of the housing in order to develop the image.

26 Claim, 7 Drawing Figures BACKGROUND OF THE INVENTION This inventionrelates in general to developing latent electrostatic images and, inparticular, relates to an apparatus for centrifugally bringing developermaterial into contact with a photosensitive surface in order to developa latent electrostatic image thereon.

More specifically this invention relates to a development device whereindeveloper is lifted from a sump by centrifugal force to a latentelectrostatic image to be developed to convey developer in multipledirections past the surface on which the image is positioned. Thedeveloper is conveyed to the image by being centrifugally impelledagainst the sloped inner surface of a rotating housing to move thereon.

In the process of xerography, the xerographic plate comprising a layerof photoconductive material on a conductive backing is given an uniformelectric charge on its surface and then is exposed to the subject matterto be reproduced by various projection techniques. This exposuredischarges the plate in accordance with the light intensity reaching itthereby creating a latent electrostatic image on or in the plate.Development of the image is effected by developers which may comprise,in general, a mixture of suitable, pigmented or dyed, resin base powder,hereinafter referred to as toner, which is brought into contact with theplate by various wellknown development techniques. During suchdevelopment of the image, the toner powder is brought into surfacecontact with the photoconductive coating and is held thereelectrostatically in a pattern corresponding to the latent electrostaticimage. Thereafter, the developed xerographic image may be transferred toa support material to which it may be fixed by any suitable means suchas heat fusing.

Various development devices have been utilized in xerography to developan electrostatic image formed on a photoconductive surface. Onewell-known technique of development is disclosed in the U.S. Pat. No.2,573,881 to Walkup et al. wherein toner carried by carrier particles isrolled or cascaded over the electrostatic image bearing surface. Thecarrier and toner materials are selected so that a triboelectricattraction exists between them causing the two particles to clingtogether and acquire an opposite charge. Each carrier has numerous tonerparticles attracted thereon allowing them to be transported into contactwith the photoconductive surface where the greater electrostaticattraction of the latent image will overcome the triboelectricattraction between the two developer components causing toner to bestripped off the carrier and electrostatically bonded to the chargedimage to effect development.

Another suitable manner of developing a latent electrostatic image is bycreating a cloud of toner which comes into contact with thephotoconductive surface. This mode of developing is disclosed in U.S.Pat. No. 2,928,575 to Carlson wherein a powder cloud is created in agenerator by air pressure and an electrostatic charge is placed on thetoner by contact of the cloud with the wall of the generator. Thecharged particles in cloud form thereupon are moved in the vicinity ofthe latent electrostatic image for development thereof. Therefore, inpowder cloud development the charged toner comes into contact with theimage without being affixed to a carrier at the time of development.Besides cascade and powder cloud techniques many other modes ofdevelopment are utilized in the art. Among these are: magnetic brushdevelopment as disclosed in U.S. Pat. No. 3,176,652 to Mott et al.;doner development as disclosed in U.S. Pat. No. 3,216,844 to King; furbrush development as disclosed in U.S. Pat. No. 3,251,706 to Walkup andthe like.

Several difficulties are associated with the previous methods ofdevelopment. Cascade development, for example, presents a problem indeveloping large area images. Generally, the electric field of anelectrostatic image is stronger at the edges than in the centralportion. Therefore, the lines of force at the edges are sufiicient toattract toner from the carrier, but in the central portion the toner isnot attracted to the image since the field is not strong enough toovercome the triboelectric attraction of the two components of thedeveloper. Such a phenomena will result in incomplete development in thecentral portions of an image while the edges normally are sufficientlydeveloped.

Cascade development also requires a thorough intermixing of thedeveloper after repeated development of an image. If inter-mixing doesnot occur, a defect in development appearing an image striations willresult, because of localized carrier material becoming depleted of tonerpowder. Since images normally have varying size latent image areas to bedeveloped along the direction of flow, repeated development causes thedeveloper flow moving past the more massive image areas to be depletedof toner in a greater amount than the less massive image areas causingcertain areas of the developer flow to be depleted of toner more thanothers. Elaborate systems for inter-mixing of developers, therefore, arerequired to overcome this toner depletion difficulty.

The aforementioned powder cloud development technique does overcomelarge area development problems as presented by cascade developmentsince toner is presented to the electrostatic image without beingaccompanied by carrier particles. Therefore, the electrostaticattraction of the latent image does not have to compete with thetriboelectric attraction between toner and carrier which allows thetoner to more readily affix to the weaker attraction of the centralportion. However, powder cloud development suffers from other drawbacksincluding a tendency to develop the non-image background areas of thephotoconductive surface. A photoconductive surface contains residualcharge in areas other than the image area and the toner in a powdercloud unaccompanied by carrier particles will develop the so-calledbackground area because the residual electrostatic field remaining afterexposure of the photoreceptor does not have to compete with thetriboelectric attraction between the development particles as in acascade system. Further, the generation of high velocity toner cloudflow conditions in prior art powder cloud devices causes directionaldevelopment defects which appear as streaks in the developed image,since the toner passes the photoconductive surface in only onedirection.

Therefore, it becomes desirable in xerography to provide an improveddevelopment apparatus which overcomes many of the aforementionedproblems presented by the prior art development means. For example, suchan improved device should adequately develop solid image areas with aminimum of toner starvation of the carrier particles as usually producedby the cascade technique of development. Further, it is advantageousthat an improved development device be provided which does not producedirectional effects such as streaking of an image.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto develop a latent electrostatic image with an improved apparatus.

Another object of this invention is to improve the development of thesolid areas of a latent electrostatic image.

A further object of this invention is to eliminate elaborate developerconveying and inter-mixing systems in a development apparatus. I

Still another object of this invention is to present developer to thelatent electrostatic image area in multiple directions.

A still further object of this invention is to improve a developmentapparatus by presenting developer to a latent electrostatic image areain a more uniform flow pattern.

Another object of this invention is to better develop a latentelectrostatic image with a magnetic field inducing device in adevelopment apparatus.

These and other objects are obtained in accordance with the presentinvention wherein there is provided an effective and inexpensivedevelopment device which overcomes many of the aforementioneddifficulties presented by the cascade, powder cloud, and otherdevelopment systems. The invention comprises a non-complicated systemhaving but one moving part and a self-circulating developer feature. Thenovel development devices disclosed herein will efficiently overcomesolid area development problems of the cascade method as well asminimize the formation of image striations. The latter problem is solvedbecause developer is conveyed past the image area on the photoreceptorin multiple directions and toner depletion in specific areas ofdeveloper flow is thereby kept to a minimum. Therefore, elaboratedeveloper inter-mixing means necessary in the cascade technique ofdevelopment is not required by the present invention. Further, many ofthe problems presented by use of the powder cloud technique arealleviated by the development devices of the invention because a twocomponent developer as well as development electrode means is utilizedin the present invention to aid in overcoming such difficulties asundesired development of non-image areas inherent in powder clouddevices.

The novel devices described herein accomplish these results bycentrifugally conveying developer material to a surface bearing a latentelectrostatic image to be developed. A rotating housing is the essentialmoving part of the invention and included in the devices disclosedherein is a self-circulating developer feature. Also, the presentinvention overcomes solid area and background difficulties by utilizinga surface of the centrifugal developer conveying means as a developmentelectrode to increase the lines of electrostatic force of the centralportion of the image area. Further, the high flow velocities inherent inthe instant centrifugal development apparatus has been found to preventsticking or beading" of carrier beads to the charged image or otherareas of the photoconductive surface as occasioned in the use of othertwo component developer systems such as in cascade devices.

DESCRIPTION OF THE DRAWING Further objects of this invention togetherwith additional features contributing thereto and advantages accruingtherefrom will be apparent from the following description of severalembodiments of the invention when read in conjunction with theaccompanying drawings wherein:

FIG. l is a schematic illustration ofa belt type xerographic machineutilizing the development device of the present invcntion;

FIG. 2 is a perspective illustration of one embodiment of thedevelopment device according to the present invention;

FIG. 3 is a schematic illustration of the embodiment of the inventionillustrated in FIG. 2;

FIG. d is a schematic illustration of a second embodiment of thedevelopment device according to the present invention;

FIG. 5 is a schematic illustration of another embodiment of thedevelopment device according to the present invention;

FIG. 6 is a schematic illustration of another embodiment of thedevelopment device according to the present invention; and

FIG. 7 is a perspective illustration of the flow of developer past asurface bearing a latent electrostatic image according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there isshown a schematic view of a belt type xerographic machine utilizing thedevelopment devices of the present invention. The essential element ofthe machine is a belt I mounted on suitable rollers and drivable in aconventional direction by a motor (not shown). The belt 1 comprises anouter surface with a layer on photoconductive insulating material suchas vitreous selenium or other suitable surface. An uniform electrostaticcharge is placed on the photoconductive surface of the belt 1 by meansof a conventional corona charging device 2. The uniformly chargedsurface on the belt is then moved to exposure means 3, which may be anywell-known device which will expose the charged surface to copy to bereproduced and form a latent electrostatic image of the copy on thephotosensitive belt surface.

Following the formation of a latent electrostatic image of the copy, theimage on the belt will move to the development device 10 according tothe present invention (to be described in detail later) to bring thelatent image into contact with developer material for developmentthereof. After development, the visible image moves to a transfer means4 and is transferred from the belt to a web of paper 5 or the like whichis positioned in contact with the belt by rollers 6. A second coronacharge device 7 applies a charge to the back of the web 5 to facilitatetransfer of the toner powder in image form. The toner image on the webthen moves past a heating element 8 which permanently affixes the tonerto the paper web to form a duplicate of the original copy. A rotatingbrush 9 contacts the belt surface after it moves past the transferdevice 4 to remove any residual image material on the surface prior to asubsequent reproduction cycle. It is clear that other modes of charging,exposing, transfer, or fusing may be utilized in connection with thepresent invention.

Referring now to FIGS. 2 and 3, there is illustrated a first embodimentof the development device 10 shown in FIG. 1 according to the presentinvention. In particular in FIGS. 2 and 3, there is shown a rotatinghousing 111 journalled on a vertical shaft 12 surrounded by sleeve 13which is connected to a base plate M by use of threads. Sealed ballbearings 16 are located at both ends of the sleeve 13 to surround theshaft 12 to allow rotation of the shaft relative to the sleeve. Theshaft 12 is journalled at one end by bearings 16 and is connected to aflexible drive belt 17 adjacent thereto. The flexible belt 17 isconnected to a conventional variable speed motor M that is mounted onbrackets (not shown) beneath the base plate 14 which effects rotation ofthe shaft.

A cover member 118 is affixed to the upper end of the shaft by suitablemeans to substantially close the upper portion of the housing lllwherein an opening 18a is provided between the periphery of the coverand the top of the housing to allow developer flow therebetween. A vanesupport member 1812 is surroundingly affixed by suitable means to a hubportion of.

the cover member to receive and retain a series of vane members 19. Thevane members are shown in FIGS. 2 and 3 for convenience of illustrationas two flat vertically oriented vanes although the vane members maycomprise other numbers and other oriented shapes, as for example,helical forms and the like. The vane member 19 extends radially from thevane support member 18 to the inner surface 20 of the wall 21 of thehousing ill and is fixed thereto in slots 22. The vanes extendvertically along the entire height of the inner surface of the housingand include at the bottom thereof scoops 23 in the form of plows whichextend below the bottom of wall means 211 and are curved into thedirection of rotation ofthe housing. The inner surface 20 is in aconical shape extending the height of the housing wall. For example, theinner wall 20 may be sloped at a 60 angle with respect to horizontal,but it should be apparent that other slopes may be utilized according tothe present invention depending on desired developer flow. The wallfurther includes a horizontal top surface 24 and a vertical outersurface 25 adjacent the top surface. The vertical outer surface 25extends partially downward to meet a horizontal under surface 26 and therest of the outer surface of the wall then comprises a sloped outersurface 27. The sloped outer surface 27 is illustrated as being slopedat a different angle with respect to the horizontal than is the innersurface wall 20, but may encompass any other desired slopes or shapes.in the construction thus far described, it should be apparent that thehousing wall 21, the vanes 19, and the vane support member 18, and theshaft 12 all rotate unitarily about the axis of rotation of the shaftand are rotated by motor M.

An annular conductive disc member 30 which can be made of any suitableconductive material is unitarily mounted on the top surface of thehousing and is of a height to allow flow through the opening 18a. Theinner surface 31 of the annular disc is sloped correspondingly to theinner conical surface to be a mere extension thereof. The top surface 32of the annular disc is sloped outwardly at a slight angle with respectto the horizontal. For example, one construction of the novel devicedisclosed herein extended a width of two inches from the inner edge tothe outer edge of the top surface of the annular disc. The outer edge ofthe disc in such a form was elevated 30/ l ,000 of an inch from theelevation of the inner edge of the surface.

The annular disc is electrically grounded through the. wall of thehousing, vanes, vane support member and shaft thereby acting as adevelopment electrode to increase the lines of force emanating from thelatent electrostatic image. The annular disc, the housing wall 21, vanes19, vane support member 18 and shaft 12 are formed of a suitableconductive material such as a metal to allow the disc to be groundedthrough the body of the device. However, the materials used inconstruction of these latter mentioned elements is not intended to belimited to a conductive material, and it is within the scope of thisinvention to use suitable non-conductive materials for one or more ofthese elements. In such a case the annular disc 30 may be groundeddirectly in a conventional manner (not shown). Also, the annular discmay be biased by an electrical potential (not shown) to further modifythe electrical field of the latent image to better develop a solid imagearea or to control the deposit of toner in the background nonimage areasof the surface.

The belt 1 having an outer layer of photoconductive material with anelectrostatic image to be developed thereupon is spaced a small distancefrom the annular top surface 32. The latent image confronts the topannular surface along a substantially horizontal plane and movesrelative to the housing 11. The novel developer device of the presentinvention includes a developer catching wall 33 which will receivedeveloper flow (to be described later) as it comes ofi the top annularsurface and guides unused developer by gravity to the base plate 14. Thebase plate 14 acts as a support or sump for the developer material to becirculated and the developer supported thereby is preferably a twocomponent developer comprising carrier and toner such as, for example,disclosed in the U.S. Pat. No. 2,618,551 to Walkup. A sufficient amountof developer is retained by the base plate to insure uniform andadequate circulation of the carrier and toner particles.

In operation of the embodiment in FIG. 2, the shaft, vane supportmember, vane wall, and the annular member rotate together as a one piecehousing driven by the motor M. The developer which is supported on thebase plate 14 is picked up by scoops 23 on the vanes 19 upon rotation ofthe housing. The scoops are shaped so that their movement will pick updeveloper and place it in contact with the sloped inner surface 20. Therotation of housing causes the developer in contact to be hurled uponthe inner surface by centrifugal force. Since the inner surface issloped, a vertical force component is applied to the particles by therotation which results in the particles moving up the wall to theannular top surface 32. The annular top surface is nearly horizontiallyoriented and, therefore, he developer is hurled in all directions acrossthe annular surface in the space between it and the photoreceptorsurface. The uniformity of the developer flow across the annular disc isincreased by the cover member 18 which insures that flow only isdirected through the opening 18a between the cover and the annular disc.As illustrated in FIG. 7, the flow across the annular disc is notperfectly radial because the rotation of the housing normally causes thedeveloper to leave the annular surface at an angle to the radialdirection.

Since the space between the annular disc and the charged image is small,flow of developer between the two elements causes toner to be in contactwith the latent image to thereby affix toner thereto. The top annularsurface is sloped slightly in the direction of flow, as previouslydiscussed, to maintain or increase the interference of the developermaterial with the photoconductive surface as well as to controldeveloper flow.

It is advantageous to slope the upper annular surface because the flowarea increases as the circumference of the disc becomes greater in anoutward direction and, therefore, the slope surface will act to maintaindeveloper flow density approximately constant. The developer willcontact the charged image from multiple directions as most clearlyillustrated in FIG. 6, because of the substantial radial flow across theannular surface and the movement of the belt relative thereto. As aresult, the problem of toner depletion of the'carrier particles asexperienced in the cascade process is reduced to a minimum sincespecific parts of the image are not exposed only to one specific area ofdeveloper flow.

The unused developer is caught by catching wall 33 surrounding theannular surface and by gravity returns to base plate 14 to berecirculated. Therefore, the development apparatus of the inventionincludes a self-circulating feature to return unused developer to thesump for subsequent use which alleviates expensive circulating means ofprior art development devices. Further, it is within the scope of thepresent invention to use any desired slope angle of the inner surface orrotational speed of the housing which affords suitable developmentresults depending on presented conditions. Furthermore, the innersurface need not be limited to one uniform slope and can comprise asurface having two or more slope angles or other shaped surfaces suchas, for example, an elliptical profile.

Referring now in particular to FIG. 4, there is illustrated anotherembodiment of the development device according to this invention. Thisembodiment is identical to the embodiment shown in FIGS. 2 and 3, exceptit further includes developer agitation or turbulence inducing meanscomprising a roughened upper surface 40 of the annular disc 30. In FIG.4, the roughened surface 40 is shown in the form of serrations whichtend to agitate the developer into better development contact with theelectrostatic image. Also, as an alternative or additional aid fordevelopment using the device of FIG. 4, a magnetic field is set up aboutthe annular disc by magnets 41 as shown in FIG. 4. The magnets 41 arestationary segments mounted by suitable means (not shown) beneath theannular disc 30 which allows relative motion between the electrode disc30 and the magnet, whereby a magnetic field is altemately applied tospecific areas of the rotating surface. The resulting magnetic fieldalternately applied utilizing the segmented magnets will increaseturbulence of the developer passing the latent image as well as create acompacting of the developer in contact with the image area producingmore interference of toner and carrier with the image bearing surface toeffect better development of the latent image lying thereon. Using themagnetic field as a development aid in this embodiment would require theuse of a developer material which comprises well-known ferro-metalliccarrier particles that are readily deflected by the field. Also, whenemploying the magnetic field in this embodiment as a development aid, itis desirable to use a disc 30 made of a suitable material whichminimizes Eddy current losses such as, for example, a well knownsemiconductive material.

Referring now to FIG. 5, another embodiment of the development deviceaccording to the present invention is illustrated. This embodiment isidentical to the embodiment in FIGS. 2 and 3 except it includes analternative means for inducing a magnetic field about the annular discsurface. The magnetic field in this embodiment is produced by annulardisc magnet 42 mounted by suitable means (not shown) to the bottomsurface of the disc 30 to rotate therewith. The annular disc magnet 42creates an annular magnetic field about the axis of rotation of thehousing which retards the movement of the developer flow being guidedacross the annular surface. The force field created by the annularmagnet thereby produces a barrier to impede and slow developer flowreaching the field which consequently results in developer material flownot yet reaching the barrier to also slow in velocity. The amount ofthis decrease of the developer material velocity across the disc surfacedepends on the strength of the magnetic field created by the magnet andtherefore by selecting a desired field intensity a particular velocitypattern may be selected for flow across the annular disc surface. Thusthe developer flow in this embodiment is controlled to a desired flowvelocity without the need of a physical structure to block the flowwhich may disrupt the uniform flow pattern across the annular disc.Therefore, since the flow on the disc is impeded, a backup of developerflow occurs on the disc surface to effect brush-like contact of thedeveloper thereon against the belt 1 bearing an image to be developedand thus specific areas of developer material are in contact with thephotoconductive surface for a greater length of time to produceeffective development. The developer material flowing directly in themagnetic field and impeded therein is thereafter hurled into contactwith the catching wall 33 to be returned to the sump as in theaforementioned embodiments of the invention. The annular disc anddeveloper material of this embodiment may, for example, respectivelycomprise the material previously disclosed in the embodiment of FIG. 4.

In reference to FIG. 6, there illustrated still another embodiment ofthe development device according to this invention. In particular inFIG. 6, the principal ofoperation is identical to the embodimentillustrated in FIGS. 2 and 3. However, instead of utilizing a slopedinner surface of the housing, the embodiment of FIG. 6 utilizes aplurality of slanted thin wall tubes 50 to convey the developer to thelatent image area. The tubes are supported near the lower end by supportrings 51 connected to rotating shaft 52. The tubes are of any suitablenonmetallic or metallic material such as, for example, brass and areretained at their upper end by holes 53 in a thin disc-like plate 54.The upper open ends 55 of the tubes are flush with the upper surface ofthe disc 54 to form a smooth upper surface. The disc is fixedlysupported by suitable means (not shown), on the rotating shaft and ahub-like support member 55 surrounds the shaft and extends from the topof the support rings 51 to the bottom of the disc 54 to give betterphysical support to the structure.

The shaft 52 is journalled at its bottom in a similar fashion asdescribed for the embodiment of FIG. 2 so as to be rotated by a variablespeed motor M. Rotation of the shaft in FIG. will cause the support ring51, the hub support member 55, the slanted tubes 50 and the disc 54 torotate as a unitary unit about the axis of the shaft 52. The top of thedisc is gradually elevated in an outward direction similarly to the topannular surface ofthe embodiment shown in FIGS. 2 and 3 to keep thedeveloper in development contact with the latent image lying on asurface downwardly confronting the top disc surface.

The slanted tubes 50 have a slanted opening 56 at the bottom of the tubewhich extends into the developer material supported by the base plateI4. The slanted opening faces the direction of rotation of the shaft andthereby scoops up developer comprising carrier and toner particles intothe entrance of the tube. By centrifugal force the scooped developer isimpelled against the sides of the tubes and because of their slantedorientation, the developer moves up the tube to the opening on the discmember. The developer is then hurled outwardly with a radial componentof velocity in a manner similar to that illustrated in FIG. 7 for theother described embodiments.

The developer catching means 33 and base plate of this embodiment areidentical as described in conjunction with FIGS. 2 and 3. Therefore, thethin wall tubes function to convey developer in a manner similar to theconical surface previously described. Further, the annular disc of thisembodiment can function as a development electrode, since it also may begrounded through the body of the development device or be directlygrounded. If a greater electric field was required in the area of theimage, the annular disc of this form of the invention could also beconnected to an electrical bias potential to give greater or improvedsolid area development or a suitable bias may be applied to reduce thedeposit of toner in background areas on the photoconductor.

In the above description that has been disclosed improved devices foreffectively developing a latent electrostatic image supported on axerographic photosensitive surface. The surface to be developed wasdescribed for convenience of illustration as being that of a xerographicbelt, but may be used to develop other well-known photoconductivemembers in the form of plates, drums, webs or coated papers.

While the invention has been described with reference to preferredembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its essential teachings.

What is claimed is:

1. Latent image developing apparatus comprising a support surfacebearing a latent electrostatic image to be developed,

developer material for developing said latent image when positionedadjacent to the latent image,

a housing journaled for rotation about an axis generally perpendicularto the support surface including means for containing said developermaterial for radially accelerating the material by rotating the housingand exit means for allowing accelerated developer material to travelradially outward relative to the housing in a plane generally parallelto said support surface whereby the radially accelerated developermaterial makes multiple directional contact with the support surface fordeveloping the latent image.

2. The apparatus of claim I wherein the housing is adapted to bepositioned adjacent a relatively movable image bearing surface to bedeveloped.

3. The apparatus of claim I wherein the developer material comprises atwo component developer including carrier particles and toner powder todevelop the latent image.

4. The apparatus of claim 1 further including guide means spaced fromthe support surface and generally parallel thereto for guiding radiallypropelled developer material over the support surface.

5. The apparatus of claim 4 wherein said guide means is electricallyconductive and further including an electrical bias coupled to the guidemeans for development of the latent image.

6. The apparatus of claim 4 wherein said guide means comprises anannular surface in close spaced confrontation with the image bearingsurface.

7. The apparatus of claim 6 wherein developer material flow is guidedoutwardly on the entire annular surface to contact the image bearingsurface.

8. The apparatus of claim 6 wherein said annular surface is radiallyinclined at a small angle to progressively decrease the space ofconfrontation between the image bearing surface and the annular surfacein a radial direction from the axis.

9. The apparatus of claim 6 wherein the guide means is an electricallygrounded conductive member to form a development electrode.

10. The apparatus of claim 4 wherein the guide means includes aroughened surface to agitate developer material into contact with theimage bearing surface.

11. The apparatus of claim 4 wherein the guide means includes a magneticfield means to agitate the developer material into contact with theimage bearing surface.

12. The apparatus of claim 4 wherein the housing further includes adeveloper receiving means mounted adjacent the guide means to receivedeveloper material after contacting the image bearing surface to returnunused developer material to the sump.

13. The apparatus of claim 1 wherein said housing contain ing meansincludes inner wall surfaces sloped relative to the axis of rotation tocause developer material to flow along the wall when the housing isrotated and said housing further including a sump for storing developermaterial adjacent said inner walls such that developer material movesfrom the sump along the inner walls when the housing is rotated.

14. The apparatus of claim 13 wherein the inner surfaces comprise aplurality of sloped tubular members.

15. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising conveying meansto effect a flow of developer material past an image bearing surface fordevelopment contact therewith including a disc surface carrying thedeveloper flow in multiple directions past the image bearing surface andforce field means operatively connected to the conveying means to impedethe flow of the developer material passing the image bearing surface toincrease said development contact.

16. The apparatus of claim 15 wherein the force field means applies amagnetic force.

17. The apparatus of claim 15 including means to rotate the disc surfacearound an axis extending substantially perpendicular to the imagebearing surface.

18. The apparatus of claim 17 wherein the force field means applies aforce through the disc surface to impede the flow of developer materialthereon.

19. The apparatus of claim 18 wherein the force field means applies anannular force field substantially about the center of the disc surface.

20. The apparatus of claim 19 wherein the force field means comprises amagnetic field inducing means to impede the flow of developer flow onthe disc surface to increase development contact with the image bearingsurface.

21. The apparatus of claim 20 wherein the disc surface comprises anannular member and including means to effect developer material flow inoutward directions on the annular member.

22. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising surface meansincluding a disc surface rotatably mounted about an axis substantiallyperpendicular to an image bearing surface and supporting developermaterial for development by contact with the image bearing surface,

motion inducing means operatively connected to the surface means toeffect movement thereof about said axis, and

force field inducing means including magnetic field generating meansmounted adjacent the surface means to control the development contactbetween the developer material and the image bearing surface.

23. The apparatus of claim 22 wherein the magnetic field generatingmeans creates a magnetic field about the axis.

24. The apparatus of claim 22 wherein the surface means is coupled tomeans to induce developer flow thereon in multiple directions past theimage bearing surface to be developed.

25. The apparatus of claim 24 wherein force field means controls thedeveloper material by impeding the flow of developer material 'on thesurface means.

26. A method of developing latent electrostatic images comprisingradially propelling developer material from a housing journaled forrotation about an axis generally perpendicular to a support surfacebearing a latent electrostatic image to be developed and directing thedeveloper material over the latent image during its radial travel in aplane generally parallel to the support surface to obtain multipledirection contact between the developer material and support surface.

1. Latent image developing apparatus comprising a support surfacebearing a latent electrostatic image to be developed, developer materialfor developing said latent image when positioned adjacent to the latentimage, a housing journaled fOr rotation about an axis generallyperpendicular to the support surface including means for containing saiddeveloper material for radially accelerating the material by rotatingthe housing and exit means for allowing accelerated developer materialto travel radially outward relative to the housing in a plane generallyparallel to said support surface whereby the radially accelerateddeveloper material makes multiple directional contact with the supportsurface for developing the latent image.
 2. The apparatus of claim 1wherein the housing is adapted to be positioned adjacent a relativelymovable image bearing surface to be developed.
 3. The apparatus of claim1 wherein the developer material comprises a two component developerincluding carrier particles and toner powder to develop the latentimage.
 4. The apparatus of claim 1 further including guide means spacedfrom the support surface and generally parallel thereto for guidingradially propelled developer material over the support surface.
 5. Theapparatus of claim 4 wherein said guide means is electrically conductiveand further including an electrical bias coupled to the guide means fordevelopment of the latent image.
 6. The apparatus of claim 4 whereinsaid guide means comprises an annular surface in close spacedconfrontation with the image bearing surface.
 7. The apparatus of claim6 wherein developer material flow is guided outwardly on the entireannular surface to contact the image bearing surface.
 8. The apparatusof claim 6 wherein said annular surface is radially inclined at a smallangle to progressively decrease the space of confrontation between theimage bearing surface and the annular surface in a radial direction fromthe axis.
 9. The apparatus of claim 6 wherein the guide means is anelectrically grounded conductive member to form a development electrode.10. The apparatus of claim 4 wherein the guide means includes aroughened surface to agitate developer material into contact with theimage bearing surface.
 11. The apparatus of claim 4 wherein the guidemeans includes a magnetic field means to agitate the developer materialinto contact with the image bearing surface.
 12. The apparatus of claim4 wherein the housing further includes a developer receiving meansmounted adjacent the guide means to receive developer material aftercontacting the image bearing surface to return unused developer materialto the sump.
 13. The apparatus of claim 1 wherein said housingcontaining means includes inner wall surfaces sloped relative to theaxis of rotation to cause developer material to flow along the wall whenthe housing is rotated and said housing further including a sump forstoring developer material adjacent said inner walls such that developermaterial moves from the sump along the inner walls when the housing isrotated.
 14. The apparatus of claim 13 wherein the inner surfacescomprise a plurality of sloped tubular members.
 15. An apparatus fordeveloping a support surface bearing a latent electrostatic image withdeveloper material comprising conveying means to effect a flow ofdeveloper material past an image bearing surface for development contacttherewith including a disc surface carrying the developer flow inmultiple directions past the image bearing surface and force field meansoperatively connected to the conveying means to impede the flow of thedeveloper material passing the image bearing surface to increase saiddevelopment contact.
 16. The apparatus of claim 15 wherein the forcefield means applies a magnetic force.
 17. The apparatus of claim 15including means to rotate the disc surface around an axis extendingsubstantially perpendicular to the image bearing surface.
 18. Theapparatus of claim 17 wherein the force field means applies a forcethrough the disc surface to impede the flow of developer materialthereon.
 19. The apparatus of claim 18 wherein the force field meansapplies an annular force field substaNtially about the center of thedisc surface.
 20. The apparatus of claim 19 wherein the force fieldmeans comprises a magnetic field inducing means to impede the flow ofdeveloper flow on the disc surface to increase development contact withthe image bearing surface.
 21. The apparatus of claim 20 wherein thedisc surface comprises an annular member and including means to effectdeveloper material flow in outward directions on the annular member. 22.An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising surface meansincluding a disc surface rotatably mounted about an axis substantiallyperpendicular to an image bearing surface and supporting developermaterial for development by contact with the image bearing surface,motion inducing means operatively connected to the surface means toeffect movement thereof about said axis, and force field inducing meansincluding magnetic field generating means mounted adjacent the surfacemeans to control the development contact between the developer materialand the image bearing surface.
 23. The apparatus of claim 22 wherein themagnetic field generating means creates a magnetic field about the axis.24. The apparatus of claim 22 wherein the surface means is coupled tomeans to induce developer flow thereon in multiple directions past theimage bearing surface to be developed.
 25. The apparatus of claim 24wherein force field means controls the developer material by impedingthe flow of developer material on the surface means.
 26. A method ofdeveloping latent electrostatic images comprising radially propellingdeveloper material from a housing journaled for rotation about an axisgenerally perpendicular to a support surface bearing a latentelectrostatic image to be developed and directing the developer materialover the latent image during its radial travel in a plane generallyparallel to the support surface to obtain multiple direction contactbetween the developer material and support surface.